The present invention relates generally to medical devices and methods. More specifically, the present invention relates to vibrational catheter devices and methods for treating occlusive intravascular lesions.
Catheters employing various types of vibration transmitting members have been successfully used to ablate or otherwise disrupt obstructions in blood vessels. Specifically, ablation of atherosclerotic plaque or thromboembolic obstructions from peripheral blood vessels such as the femoral arteries has been particularly successful. Various vibrational catheter devices have been developed for use in ablating or otherwise removing obstructive material from blood vessels. For example, U.S. Pat. Nos. 5,267,954 and 5,380,274, issued to an inventor of the present invention and hereby incorporated by reference, describe ultrasound catheter devices for removing occlusions. Other examples of ultrasonic ablation devices for removing obstructions from blood vessels include those described in U.S. Pat. Nos. 3,433,226 (Boyd), 3,823,717 (Pohlman, et al.), 4,808,153 (Parisi), 4,936,281 (Stasz), 3,565,062 (Kuris), 4,924,863 (Sterzer), 4,870,953 (Don Michael, et al), and 4,920,954 (Alliger, et al.), as well as other patent publications W087-05739 (Cooper), W089-06515 (Bernstein, et al.), W090-0130 (Sonic Needle Corp.), EP316789 (Don Michael, et al.), DE3,821,836 (Schubert) and DE2438648 (Pohlman). While many vibrational catheters have been developed, however, improvements are still being pursued.
Typically, a vibrational catheter system for ablating occlusive material includes three basic components: an vibration energy generator, a transducer, and a vibrational catheter. The generator converts line power into a high frequency current that is delivered to the transducer. The transducer contains piezoelectric crystals which, when excited by the high frequency current, expand and contract at high frequency. These small, high-frequency expansions (relative to an axis of the transducer and the catheter) are amplified by the transducer horn into vibrational energy. The vibrations are then transmitted from the transducer through the vibrational catheter via a vibrational transmission member (or wire). The transmission member transmits the vibrational energy to the distal end of the catheter where the energy is used to ablate or otherwise disrupt a vascular obstruction.
To effectively reach various sites for treatment of intravascular occlusions, vibrational catheters of the type described above typically have lengths of about 150 cm or longer. To permit the advancement of such vibrational catheters through small and/or tortuous blood vessels such as the aortic arch, coronary vessels, and peripheral vasculature of the lower extremities, the catheters (and their respective ultrasound transmission wires) must typically be sufficiently small and flexible. Also, due to attenuation of ultrasound energy along the long, thin, ultrasound transmission wire, a sufficient amount of vibrational energy must be applied at the proximal end of the wire to provide a desired amount of energy at the distal end.
One continuing challenge in developing vibrational catheters for treating vascular occlusions is to provide adequate vibrational energy at the distal end of a catheter device while simultaneously minimizing stress on the vibrational transmission wire in the area where it connects with the transducer. Typically, the vibrational transmission wire is coupled with the transducer via some kind of connector. A portion of the transmission wire immediately adjacent the connector is often put under great stress and strain when sufficient vibrational energy is applied to provide the desired vibration at the distal end of the catheter. This stress and strain can cause overheating and unwanted wear and tear of the transmission member, thus leading to wire breakage and a shortened useful life of the catheter device.
Some vibrational catheter devices include one or more absorption members where the proximal end of the vibrational transmission wire attaches to a transducer connector. For example, one such absorption member is described in U.S. Pat. No. 5,382,228. Such absorption members, however, may have drawbacks, in that they may be prone to coming loose and disconnecting from the transducer connector, and would thus become a loosely moving body within the catheter, disrupting vibrational energy transmission and reducing the catheter's efficacy.
Therefore, a need exists for improved vibrational catheter devices and methods that provide ablation and/or disruption of obstructions in lumens, such as vascular lumens. Ideally, such vibrational catheters would provide a desired level of power at a distal end of the device while also preventing or reducing stress and strain placed on the proximal end of the vibrational transmission member. Also ideally, such devices would be easily manufactured and have as few moving parts as possible in the area of connection of the transmission member with the transducer connector. At least some of these objectives will be met by the present invention.